IR thermographic detection and characterization of hidden corrosion in metals: General analysis

Principles of infrared thermographic non-destructive testing for determining hidden corrosion in metals are summarized and discussed. 1D, 2D and 3D heat conduction models are introduced to simulate thermal processes in corroded areas. In thick metals, the lateral heat dissipation is mainly responsible for significantly smoothing the temperature contrast curves. Modelling small-size corroded sites requires 3D numerical models. Numerous defects have been simulated and the inversion formulas for determining material loss have been modelled for both flash and square-pulse heating. It has been shown that corrosion characterization inaccuracy is lower than 20% in cases representing a practical interest.     

Viscous flow of a Newtonian fluid in a curved channel with flexible moving porous walls

We consider flow of a viscous Newtonian fluid in a curved channel with moving porous walls; the upper wall is flexible and its position in unknown a priori. This work is motivated from a papermaking application namely roll forming. We solve the leading order terms in equations of motion using perturbation methods and present analytical expressions for the variation in channel size, pressure, and viscous shear. The stability of the solution is also examined and we report the conditions for marginal stability.     

A generalised model for cheese mass loss determination during ripening

A generalised mechanistic model describing cheese mass loss during ripening in controlled conditions is proposed. It is based on two main processes occurring in the cheese rind: respiratory activity of the microbial consortia and water evaporation. The generalisation is based on (i) two different cheesemaking methods and cheese sizes (Camembert, a soft cheese and Saint-Nectaire, a pressed non-cooked cheese), (ii) several trials performed at ranging controlled ripening temperatures (7-16 °C) and relative humidities (88-98%) and (iii) different ripening room sizes and air flow patterns. Some hypothesis underlying this generalisation are discussed. The model fits the experimental data accurately: the absolute mean error is lower than 11% of the experimental cheese mass loss. The two main factors governing the water transfer rate are the ripening room relative humidity and the cheese surface water activity. Their impact on the model accuracy is about 40% and 20%, respectively.     

Polymer additive migration to foods-a direct comparison of experimental data and values calculated from migration models for polypropylene

To reduce the amount of compliance testing for food contact polymers the use of migration modelling is under discussion and being evaluated by an EU Commission funded project (Evaluation of Migration Models No. SMT4-CT98-7513). The work reported in this paper was exclusively funded by industry to provide data for the independent evaluation of a diffusion based model using eight different samples of polypropylene (PP) covering the range of polymers specification and five commonly used plastics additives. One hundred and fifty experimental migration data have been obtained in triplicate and used to evaluate a Fickian-based migration model in the prediction of specific migration of five additives into olive oil. All tests were conducted using olive oil, representing the most severe case for fatty foods, with test conditions of 2h at 121 ° C, 2h at 70 ° C and 10 days at 40 ° C, representing short term exposures at high temperatures and room temperature storage. Predicted migration values were calculated using the Piringer 'Migratest Lite' model by entering the measured initial concentration of additive in the polymers(C_p,0) in to the equations together with known variables such as additive molecular weight, temperature and exposure time. Where necessary the data generated in this study have been used to update the model. The results indicate the Piringer migration model, using the 'exact' calculations of the Migratest Lite program, predicted migration values into olive oil close to, or in excess of, the experimental results for > 97% of the migration values generated in this study. For all measurements, the predicted migration from the Migratest Lite program was greater than 70% of the observed value. This study has identified the possibility that random co-polymers of propylene and ethylene give higher migration than other grades of polypropylenes and could be treated as a separate case. However, further work on more samples of random co-polymers is required to confirm this finding.     

Modelling of granulation by a two-stage auto-layering mechanism in continuous industrial drums

A mechanistic model for the granulation of particulate materials with a wide size distribution in a large-scale continuous drum is presented. It takes cognizance of the effect of relevant process variables: feed size distribution, moisture content, binders such as lime, residence time distribution, feed rate, etc. The model is based on the auto-layering mechanism of granule growth and incorporates a piecewise linear model for granulation kinetics. Laboratory scale tests on a batch drum are used to provide kinetic parameters. The size-dependent residence time distribution of agglomerating mass in the continuous drum is represented by a combination of mixed and plug flow regimes operating in parallel. The model is customized for a continuous drum in an iron ore fines sintering plant. The predicted granule size distributions are in good agreement with the plant data under widely varying operating conditions. The modelling framework provides scope for modifying the individual modules for drum residence time distribution or the granulation mechanism and growth kinetics.     

Hydrogen generation in a Pd membrane fuel processor: Productivity effects during methanol steam reforming

Performance analyses are carried out for the palladium membrane fuel processor for catalytic generation of high purity hydrogen. The reactor model includes detailed particle-scale multi-component diffusion, multiple reversible reactions, flow, and membrane transport. Using methanol steam reforming on Cu/ZnO/Al₂O₃ catalyst as the test reaction, a systematic examination of the effects of operating and reactor design parameters on key performance metrics is presented. Single particle simulations reveal a complex interplay between nonisobaric transport and the reversible reactions (methanol reforming and decomposition, and water-gas shift), which impact overall reactor performance. An analysis of characteristic times helps to identify four different productivity controlling regimes: (i) permeation control, encountered with thick membranes and/or insufficient membrane area; (ii) catalyst pore diffusion control encountered with diffusion of reacting species in larger particles; (iii) reaction control, encountered when intrinsic catalytic rates are too low because of inadequate activity or catalyst loading; and (iv) feed control, encountered when the limiting reactant feed rate is inadequate. The simulations reveal that a maximum in the hydrogen productivity occurs at an intermediate space velocity, while the hydrogen utilization is a decreasing function of space velocity, implying a trade-off between productivity and hydrogen utilization. The locus of productivity maxima itself exhibits a maximum at an intermediate membrane surface to volume ratio, the specific value of which is dependent on the particle size, membrane thickness and reaction conditions. At moderate temperature and total pressure (, 10 bar), particles smaller than 2 mm diameter, Pd membranes with thickness less than , and membrane surface to volume ratio exceeding are needed to achieve viable productivity . A comparison between the packed-bed membrane reactor and conventional packed-bed reactor indicates a modest improvement in the conversion and productivity due to in situ hydrogen removal.     

多层组合钢框架建筑的三维非线性动力连续性倒塌分析——参数研究

采用3维有限元模型进行多层组合钢框架建筑的连续性倒塌分析。当柱突然倒塌时,该模型可以反映多层建筑的整体3维性能。基于该模型,用于分析不同材料的结构性能的参数:结构钢的强度,混凝土的强度和钢筋网格尺寸。通过参数分析,给出延缓连续性倒塌的设计措施。     

外包混凝土组合钢柱的偏心受压分析

给出了偏心受压下外包混凝土组合钢柱的3维非线性模型。该组合柱两端铰接,沿主要轴线方向施加一个偏心力。此偏心率的范围在柱截面总高度的0.125～0.375之间。该模型考虑钢、混凝土、纵向和横向钢筋的非弹性性能,以及组合柱中混凝土的约束作用。考虑了钢与混凝土之间、纵向与横向钢筋之间、钢筋与混凝土之间交界面粘结力,以及不同材料对组合柱抵抗变形所起的作用。该模型考虑了初始几何缺陷。已有的试验数据证明了模型的有效性。混凝土强度等级为30～110MPa。钢截面的屈服应力为275～690MPa。通过改变偏心率、柱的尺寸、结构钢尺寸与屈服应力值和混凝土强度,以确定其对偏心受压下组合柱性能的影响。结果显示,结构钢屈服应力的增加对组合柱强度的影响较大,尤其当柱的偏心率为0.125D时。当柱的偏心率为0.375D且混凝强度低于70MPa时,结构钢屈服强度的变化对柱强度影响较大。将数值分析所得组合柱的强度与设计规范Eurocode4的计算结果进行比较。结果表明,Eurocode4准确地计算出偏心组合柱强度,但是估算的弯矩过大。     

实施CIM的评价准则

计算机集成制造（ＣＩＭ）在国际上已经实施２０多年了。我国的ＣＩＭ研究工作也已经开展了１０年。国际上对ＣＩＭ的看法众说纷纭，据国外的某些统计报道，有的企业实施ＣＩＭ取得了巨大成果，而更多的企业实施效果却不理想。如何评价企业实施ＣＩＭ的必要性和正确性已成为这一领域的重要课题。然而，由于其本身的复杂性，迄今为止，在文献中还找不到可以适用于多数ＣＩＭ企业、又为大家普遍接受的评价方法。我们总结了近年来在国内的ＣＩＭ实践，又基于中欧合作对ＣＩＭ方法论的研究，在此提出一套ＣＩＭ评价的准则和方法，希望它能在企业作出实施ＣＩＭ的决策时，对企业有一定的引导作用。     

Changes in atmospheric corrosion rate caused by chloride ions depending on rain regime

Plain carbon steel and copper samples were exposed in two atmospheric test stations located in Havana, Cuba and Medellin, Colombia. Samples were submitted to accelerated outdoor test by intermittent spraying of a salt solution (SCAB test) according to ISO 11474:98.A remarkable difference in the acceleration rate of chloride ions for mild steel and copper between Cuban and Colombian stations was determined. Differences in rain amount and frequency between Havana and Medellin are noticeable. The influence of rain seems to be important in determining the acceleration rate of chloride ions on steel and copper due to its washing effect. A model for the influence of the interaction between rain characteristics and chloride deposition rate on mild steel and copper corrosion behaviour with time is proposed. Data fit very well to the proposed model. It is concluded that rain regime should be taken into account in order to determine the real acceleration rate caused by chloride ions in atmospheric conditions.